On the day of the new quarter the shadow cast by the higher stone moves across the lower stone, which stands 3.6m away.
The animation shows the new quarter based on the Vernal Equinox defined as 1) “Heigth model equinox”, and 2) “Refraction equinox”. see definitions in Days-of-the-calendar.
The gradient of the top of the stones are in good alignment with the sun’s path.
The higher stone’s inclination and height were adjusted (-0.17m och 13.5°). Thick roots from a tree standing only 1m from the higher stone most probably has lifted the stone from its original position. This made a height adjustment necessary. The lower stone were adjusted 3°. The calculation of the adjustments were done in a way to make the three nearest stones fit important calendar days. It was possible to find days with good precision for all the three stones: 1) vernal/autumnal equinoxes, 2) vernal new quarter, and 3) summer solstice. You can find the two other sunlines here:
The big adjustments makes it impossible to decide if the sunline shows exactly the correct day.
Since one stone is leaning and its height has been changed the shadow will not be in the correct position to show the vernal and autumnal equinoxes.